A vehicle differential device (differential gear) including a differential case rotatably supported via a bearing by a housing and a drive shaft inserted into the differential case is used in a power transmission path of various vehicles. The differential device includes, for example, a ring gear having outer circumferential teeth and disposed in the housing; the differential case integrally disposed with the ring gear and rotating around one shaft center; a pinion gear rotatably supported around a shaft center orthogonal to the one shaft center by a pinion shaft fixed to the differential case within the differential case; and a pair of side gears facing each other with the pinion gear interposed therebetween and disposed rotatably relative to each other around the one shaft center within the differential case, and the differential device allocates a drive force to a pair of drive shafts (axles) corresponding to left and right drive wheels coupled to the pair of the side gears while allowing differential rotation.
The differential device as described above is required to supply sufficient oil to portions in need of lubrication. To implement the lubrication, for example, techniques have been proposed such as a lubricating structure of a differential device described in Patent Document 1. According to this technique, lubrication oil can stably be ensured from low rotation to high rotation to improve lubrication performance by introducing the oil into a chamber and guiding and supplying the oil dripping from an opening by an oil guide to rear surface portions of bearings to lubricate the bearings and an inboard portion (differential case).